Exfoliation of graphene by multilayer coextrusion

ABSTRACT

Exfoliation of graphene from graphite using multilayer coextrusion is generally disclosed. In some example embodiments, graphite may be dispersed within a first processing material, and the first processing material and a second processing material may be co-extruded through a plurality of series coupled layer multiplication dies to exfoliate graphene from the graphite. The graphene may be separated from the resulting multi-layered material. In some example embodiments, graphite flake and/or expanded graphite may be dispersed within the first processing material.

BACKGROUND

The present disclosure generally pertains to production of graphene fromgraphite and, more particularly, to exfoliation of graphene fromgraphite using multilayer coextrusion.

SUMMARY

Exfoliation of graphene from graphite using multilayer coextrusion isgenerally disclosed. In some example embodiments, graphite may bedispersed within a first processing material, and the first processingmaterial and a second processing material may be co-extruded through aplurality of series coupled layer multiplication dies to exfoliategraphene from the graphite. The graphene may be separated from theresulting multi-layered material. In some example embodiments, graphiteflake and/or expanded graphite may be dispersed within the firstprocessing material.

Apparatuses for producing graphene from graphite are generallydescribed. Some example apparatuses may include multilayer co-extrusiondevices comprising a plurality of series coupled layer multiplicationdies. Some example multilayer co-extrusion apparatuses may be configuredto exfoliate graphene by co-extrusion of a first processing material anda second processing material through the plurality of series coupledlayer multiplication dies to produce a resulting material including aplurality of alternating layers of the first processing material and thesecond processing material, where the first processing material maycomprise a first graphite material dispersed in a first substrate andthe second processing material may comprise a second substrate material.

Methods of producing graphene from graphite are generally described.Some example methods may include dispersing a first graphite material ina first substrate material to form a first processing material. Someexample methods may further include exfoliating graphene from the firstgraphite material by co-extrusion of the first processing material and asecond processing material through one or more layer multiplication diesto yield a resulting material including individual layers of the firstprocessing material interposed between individual layers of the secondprocessing material, the second processing material comprising a secondsubstrate material. Some example methods may also further includeseparating the graphene from the first substrate material and the secondsubstrate material.

Methods of delaminating multi-sheet substances are generally disclosed.Some example methods may include mixing a multi-sheet substancecomprising a plurality of stacked sheets with a first substrate materialto form a first processing material. Some example methods may furtherinclude delaminating one or more sheets from the multi-sheet substanceby application of shear stress to the first processing material. Someexample methods may also further include separating the one or moredelaminated sheets from the first substrate material.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several embodiments in accordance with thedisclosure and are, therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings.

In the drawings:

FIG. 1 is a block diagram illustrating an example device for producinggraphene;

FIG. 2 is a block diagram illustrating an example device for producinggraphene;

FIG. 3 is a flow chart illustrating an method of producing graphene fromgraphite; and

FIG. 4 is a flow chart illustrating an example method of delaminating amulti-sheet substance; all in accordance with at least some examples ofthe present disclosure.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here. It will be readily understood that the aspects of thepresent disclosure, as generally described herein, and illustrated inthe Figures, may be arranged, substituted, combined, and designed in awide variety of different configurations, all of which are explicitlycontemplated and make part of this disclosure.

This disclosure is drawn, inter alia, to exfoliating graphene fromgraphite. For example, shear stresses caused by multilayer coextrusionof two processing materials, at least one of which may contain graphitedispersed therein, may be used to exfoliate graphene from the graphite.

The present disclosure contemplates that graphite may be described as alayered structure in which an individual layer may be called graphene.Graphene may be described as a flat monolayer of carbon atoms tightlypacked into a two-dimensional honeycomb lattice. Graphene may beconsidered to be a basic building block for other graphitic materials.

The present disclosure contemplates that a single layer of graphene wasfirst isolated in 2004 using a so-called peeling method, which usedcellophane adhesive tape to successively remove layers from a graphiteflake. Although the flakes present on the tape may be much thicker thanone layer, a single sheet may be delaminated when the tape is liftedaway from the graphite flake. The peeling method may require a greatdeal of patience, and locating a single layer may be difficult.

Example methods according to the present disclosure may utilize shearforces produced by multilayer coextrusion of processing materials (e.g.,one or more organic polymers such as polyethylene, polypropylene,polyethylene oxide, polystyrene, or other similar polymers and/or one ormore waxes such as polyethylene wax, and/or similar substances) toexfoliate graphene from graphite. Some example methods may allowsubstantially continuous production of graphene by such multilayercoextrusion.

FIG. 1 is a block diagram illustrating an example device for producinggraphene in accordance with at least some examples described herein.Extruders 112, 114 may be configured to supply a first processingmaterial 106 and a second processing material 108, respectively, to afeed block 113. Feed block 113 may be configured to supply firstprocessing material 106 and second processing material 108 to aplurality of series coupled layer multiplication dies 116, 118, 120,122. In light of the present disclosure, it is understood that variousthermal controllers, heating devices and/or even cooling devices can bereadily adapted for use as a suitable means of precise temperaturecontrol.

An example method of producing graphene from graphite may comprisedispersing a first graphite material 102 in a first substrate material104 to form first processing material 106. First processing material 106and second processing material 108 (which may comprise a secondsubstrate material 110) may be co-extruded, such as using extruders 112,114 and/or feed block 113, through series coupled layer multiplicationdies 116, 118, 120, 122 to produce a resulting material 124 comprising aplurality of alternating layers of first processing material 106 andsecond processing material 108.

Shear stresses experienced by first processing material 106 and/orsecond processing material 108 during co extrusion through layermultiplication dies 116, 118, 120, 122 may exfoliate at least somegraphene 126 from first graphite material 102; thus, resulting material124 may comprise graphene 126. Graphene 126 may be separated fromresulting material 124, such as by at least partially dissolving firstsubstrate material 104 and/or second substrate material 110 in a solvent128 (e.g., water and/or an organic solvent). In some exampleembodiments, second processing material 108 may comprise a secondgraphite material 130, which may be dispersed in second substratematerial 110.

The present disclosure contemplates that coextruded multilayers withnumbers of layers ranging from tens of layers to thousands of layers maybe made using layer multiplication dies.

FIG. 2 is block diagram illustrating an example device for producinggraphene; in accordance with at least some examples described herein.Feed block 113 may be configured to supply first processing material 106and second processing material 108 to a plurality of series coupledlayer multiplication dies 116, 118, 120 to produce resulting material124 comprising a plurality of alternating layers of first processingmaterial 106 and second processing material 108. In some exampleembodiments, resulting material 124 may be at least partially immersedin a solvent bath 128A and/or may be subjected to a solvent spray 128Bto separate the graphene. In some example embodiments, resultingmaterial 124 may be utilized for further applications without separatingthe graphene. For example, resulting material 124 (including thegraphene) may be utilized as a concentrate that may be let down into aselected matrix.

As illustrated in FIGS. 1 and 2, first processing material 106 (whichmay comprise first graphite material 102 and/or first substrate material104) and/or second processing material 108 (which may comprise secondsubstrate material 110 and/or second graphite material 130) may bebrought together in feed block 113 to form a two layer (N=2) material.The two layer material may be forced through layer multiplication die116, which may split the two layer material into two parts (eachincluding the two layers from material 102 and material 110), and theindividual parts may be compressed, rotated, stretched, and/or stackedtogether with other individual parts. Layer multiplication die 116 mayoutput a four layer (N=4) material. Layer multiplication dies 118, 120,may likewise increase the number of layers to eight (N=8) and sixteen(N=16), respectively. In some examples, a fourth layer multiplicationdie (e.g., layer multiplication die 122 shown in FIG. 1) may be utilizedto yield a material with thirty-two (32) layers. Where individual layermultiplication dies 116, 118, 120, 122 are configured to double thenumber of layers, the number of layers of resulting material 124, N, maybe given by N=2^(n+1), where n may be the number of dies.

In some example embodiments, one or more of the layer multiplicationdies 116, 118, 120, 122 may be substantially the same as one another. Insome other example embodiments, one or more of the layer multiplicationdies 116, 118, 120, 122 may be different than one another.

In some example embodiments, after being extruded through four layermultiplication dies 116, 118, 120, 122, the individual layers of theresulting material may be about twenty (20) μm thick. Likewise, foreleven (11) series coupled layer multiplication dies, the resultingmaterial may comprise about four-thousand and ninety-six (4096) layers,where each of the individual layers of the resulting material may beabout one-hundred and fifty six (156) nm thick. Further increasing thenumber of series-coupled layer multiplication dies (e.g., about 18series couple layer multiplication dies may produce about 524,288layers) may yield a resulting material with individual layer thicknessesat about the Angstrom-level order of magnitude.

The present disclosure contemplates that feed block 113 may beconfigured to produce other numbers of layers (e.g., four layers) and/orlayer multiplication dies 116, 118, 120, 122 may be configured to tripleor quadruple the number of layers, for example.

In some example embodiments, first graphite material 102 and/or secondgraphite material 130 may comprise graphite flake and/or expandedgraphite. Turning back to FIG. 1, in some example embodiments, firstprocessing material 106 may be formed by blending first graphitematerial 102 (e.g., a powder) and first substrate material 104 (e.g., apowder) and/or feeding the blend into extruder 112 (which may be asingle and/or a twin extruder). Second processing material 108 may beformed in a similar manner using extruder 114.

In some example embodiments, first processing material 106 may beproduced by mixing first substrate material 104 and first graphitematerial 102 together. For example, powdered first substrate material104 and powdered first graphite material 102 may be combined andstirred, which may disperse first graphite material 102 in firstsubstrate material 104. In some example embodiments, first processingmaterial 106 may be extruded and/or pelletized prior to being suppliedto extruder 112. In some example embodiments, first substrate material104 and first graphite material 102 may be heated (e.g., by heatingelements and/or due to friction in an extruder) during mixing and/orduring extrusion, which may at least partially melt first substratematerial 104. Similarly, in some example embodiments, second processingmaterial 108 may be produced by mixing second substrate material 110 andsecond graphite material 130 together. In some example embodiments,second processing material 108 may be extruded and/or pelletized priorto being supplied to extruder 114 In some example embodiments, secondsubstrate material 110 and second graphite material 130 may be heated(e.g., by heating elements and/or due to friction in an extruder) duringmixing and/or during extrusion, which may at least partially melt secondsubstrate material 110.

In some example embodiments, first substrate material 104 and/or secondsubstrate material 110 may have substantially the same compositionand/or substantially similar properties. For example, in some exampleembodiments, first substrate material and/or second substrate materialmay both be at least partially soluble in the same solvent. In someexample embodiments, first substrate material 104 and/or secondsubstrate material 110 may comprise non-polar (hydrophobic) materials.For example, such non-polar materials may include paraffin waxmaterials, with or without the addition of a high molecular weightpolyolefin, which may improve processing. Such materials may be usefulfor cold extrusion (e.g., about 25 to about 40° C.). In some exampleembodiments, first substrate material 104 and/or second substratematerial 110 may comprise polar (hydrophilic) materials. For example,such hydrophilic materials may include polyethylene oxide (PEO), whichmay be useful for low temperature extrusion (e.g., about 40 to about 60°C.).

In some example embodiments, first substrate material 104 and/or secondsubstrate material 110 may have substantially different compositionsand/or properties. For example, in some example embodiments, firstsubstrate material may comprise one or more hydrophobic polymers and/orsecond substrate material may comprise one or more hydrophilic polymers.For example, one of first substrate material 104 and/or second substratematerial 110 may comprise a hydrophobic material (e.g.,polyethylene/paraffin wax blends, polystyrene, poly (4-methyl pentene)(P4MP). The other of first substrate material 104 and/or secondsubstrate material 110 may comprise a hydrophilic material (e.g.,polyethylene oxide), polyvinyl acetate, styrene acrylonitrile (SAN),poly (methyl methacrylate) (PMMA), polylactic acid, and/or blends ofthese and/or other polymers).

In some example embodiments, one or both of first processing material106 and/or second processing material 108 (which may comprise firstsubstrate material 104 and/or second substrate material 110,respectively) may comprise graphene. More specifically, in some exampleembodiments including first substrate material 104 and second substratematerial 110 having substantially the same composition and/orsubstantially similar properties, one or both of first processingmaterial 106 and/or second processing material 108 may include graphene.Similarly, in some example embodiments including first substratematerial 104 and second substrate material 110 having substantiallydifferent compositions and/or properties, one or both of firstprocessing material 106 and/or second processing material 108 mayinclude graphene.

In some example embodiments, extrusion operations may be conducted atlow temperatures (for example and without limitation, cold extrusion andlow temperature extrusion discussed above), which may contribute toincreased shear stresses within the processing material(s), which mayincrease the exfoliation of graphene from graphite. In some exampleembodiments, extrusion operations may be conducted at or near about thelowest practicable extrusion temperatures for the substrate and/orprocessing material(s).

The present disclosure contemplates that graphene produced as describedherein may be useful in the area of polymer composites, such as wherehigher strength via high aspect ratio reinforcements may beadvantageous. For example, graphene may be used in polyvinyl chloride(PVC) siding, which may increase the heat deflection temperature of thesiding such that it may better withstand hot weather-relateddeformations. As another example, poly(lactic acid), a very muchappreciated biopolymer, may be utilized in connection with graphene toimprove its performance despite its relatively low softeningtemperature. As another example, graphene may be used in automotiveand/or other transportation-related applications, where someunder-the-hood conditions may benefit from high mechanical strength andheat resistance. As another example, when used as an additive forpolystyrene-based composites, the two-dimensional geometry of graphenemay provide an extremely low percolation threshold of about 0.1%, whichmay enhance their electrical conductivity and/or the strength of thematrix.

As another example, graphene may be used to provide electricallyconductive polymers for textile applications. For example, graphene mayprovide long-lasting antistatic properties. As another example, graphenemay be useful in some electronics-related applications.

The present disclosure contemplates that processes described herein maybe used to produce substances besides graphene. For example, multilayercoextrusion processes described herein may be useful for delaminatingmulti-sheet substances comprising a plurality of stacked sheets. Forexample, the present disclosure contemplates that mica may bedelaminated into its constituent sheets using multilayer coextrusionprocesses described herein.

FIG. 3 is a flow chart illustrating an example method 400 of producinggraphene from graphite in accordance with at least some examplesdescribed herein. Method 400 may include one or more operations,functions or actions as illustrated by one or more of blocks 402, 404,and/or 406.

Processing for method 400 may begin at block 402. Block 402 may includedispersing a first graphite material in a first substrate material toform a first processing material. Block 402 may be followed by block404. Block 404 may include exfoliating graphene from the first graphitematerial by co-extrusion of the first processing material and a secondprocessing material through one or more layer multiplication dies toyield a resulting material including individual layers of the firstprocessing material interposed between individual layers of the secondprocessing material, the second processing material comprising a secondsubstrate material. In some example methods, block 404 may be followedby block 406. Block 406 may include separating the graphene from thefirst substrate material and the second substrate material.

FIG. 4 is a flow chart illustrating an example method 500 ofdelaminating a multi-sheet substance in accordance with at least someexamples described herein. Method 500 may include one or moreoperations, functions or actions as illustrated by one or more of blocks502, 504 and/or 506.

Processing for method 500 may begin at block 502. Block 502 may includemixing a multi-sheet substance comprising a plurality of stacked sheetswith a first substrate material to form a first processing material.Block 502 may be followed by block 504. Block 504 may includedelaminating one or more sheets from the multi-sheet substance byapplication of shear stress to the first processing material. Block 504may be follow by block 506. Block 506 may include separating the one ormore delaminated sheets from the first substrate material.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures aremerely examples, and that in fact many other architectures may beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality may be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated may also be viewed as being “operably connected”, or“operably coupled”, to each other to achieve the desired functionality,and any two components capable of being so associated may also be viewedas being “operably couplable”, to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents and/or wirelessly interactable and/or wirelessly interactingcomponents and/or logically interacting and/or logically interactablecomponents.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art may translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

What is claimed is:
 1. A method of delaminating a multi-sheet substance,comprising: mixing a multi-sheet substance comprising a plurality ofstacked sheets with a first substrate material to form a firstprocessing material; delaminating one or more sheets from themulti-sheet substance by application of shear stress to the firstprocessing material, application of shear stress to the first processingmaterial comprising multilayer co-extrusion of the first processingmaterial and a second processing material through one or more seriescoupled layer multiplication dies arranged to produce a resultingmaterial comprising a plurality of alternating layers comprising thefirst processing material and the second processing material uponco-extrusion of the first processing material and the second processingmaterial therethrough; and separating the one or more delaminated sheetsfrom the first substrate material.
 2. The method of claim 1, whereinmultilayer co-extrusion comprises supplying the first processingmaterial to a feed block from a first extruder, the feed block beingfluidicly coupled to the plurality of series coupled layermultiplication dies, and supplying the second processing material to thefeed block from a second extruder.
 3. The method of claim 1, wherein thefirst substrate material and the second substrate material each compriseone or more of one or more hydrophobic polymers or one or morehydrophilic polymers.
 4. The method of claim 1, wherein one of the firstsubstrate material and the second substrate material comprises one ormore hydrophobic polymers; and wherein the other of the first substratematerial and the second substrate material comprises one or morehydrophilic polymers.